Optimization of T MAC Protocol in WSN Based on Minimum Contention Window

o C l a n o it a n r e t n I 8 1 0

2 nferenceonCommunicaiton,NetworkandAritifcia lIntelilgence(CNAI2018) 8

7 9 : N B S

I -1-60595- 50 -5 6

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1_{StateK eyLaboratory fo MarineResourcesUitilzaiton ni SouthChinaSea,Haikou,Hainan,China} 2_{College fo OceanInformaitonEngineering,HainanTropicalOceanUniverstiy,}

, a y n a

S Hainan,China

3_{College fo InformaitonScience da n Technology,HainanUniverstiy,Haikou,Hainan,China}

g n i d n o p s e r r o C

* author

: s d r o w y e

K Wrieless sensor networks T-, MAC protocol, Minimum conteniton window, B ka - fc o f algortihm.

.t c a r t s b

A Considering t he issue fo energy consumption caused yb idle listening, collision n

o i s s i m s n a r t e

r a nd control consumption fo MAC layer ni wireless sensor networks, this paper c

u d o r t n

i es na improvedMACprotocolbased no et h minimumcontentionwindow no et h foundation f

o S-MAC a T-nd MAC protocol. T he proposed protocol distinctively calculates et h minimum n

o i t n e t n o

c window according ot et h position fo et h node ni et h network ot contend channe,l da n s

t s u j d

a et eh siz fo et h window yb changing et h windowcoefficient ni accordancew eitht h congestion. Combinedw ithredefinition fo et h timeinterval ' AT ' ni et T-h MAC protocol, listening da n sleeping

e m i

t si alsooptimized. T hesimulation result sdemonstratethat et h protocolproposed ni thispaper t

a r o i l e m

a es et h performanceunder et h congestion fo network ni terms fo throughput, timedelay da n y

g r e n

e consumption ot someexten,t os sa ot satisfy et h real-timetransmission da n decreaseenergy o

c nsumption.Eventually et h efficiency fo networktransmission si improved.

Introduciton

n

I WSN,both S-MAC da T-n MAC ea br ased no competitive mechanism fo MAC protocol 1[ - ]2 . e

h

T formeroperatesw a ith fixedworking/sleepi ngtimestrategyamongneighbor dno e ]s[ , n3 i which t eh synchronization mechanism si introduced ot diminish et h energy consumption caused yb et h

n o i s i l l o

c ni WSN, da tn i si achievedthrough et h w aythatnodes tg oe int sleepingwhenthere ea or n a

t a

d sending/receiving.Comparedw S-ith MAC, t eh latter ][ a4 h s tc eu t h activitytime fo sensornodes h

g u o r h

t computi eng t h active time according ot et h condition fo communication traffic w a ith y

l l a c i m a n y

d varied variable 'TA', which si related ot both sleeping a nd listening time, while n

i a t n i a

m i t eng h period unchanged, da n sends et h information w a ith burst mode ot lessen et h idle i

t p e c r e t n

i ng time 5[ -7]. However, T-MACintroduced et h problem fo increasingcontrolconsumption d

n

a earlysleep. nI view fo et h shortcomings da n deficiencies fo et T-h MACprotoco ,l na improved m

h t i r o g l

a based no et h minimum contention window si proposed ot effectively advance et h t

u p h g u o r h

t fo et h network da n reduce et h energyconsumption [8-9 .]

n o it a l u c l a

C fo MinimumConten itonWindow

e r u t a r e t i

L [ 01 ] manifests et h scienti ficbasisthat et h preferablenetworkperformance nc ea b obtained y

b dynamically computing et h size fo minimum contention window according ot et h network .

s n o i t i d n o

c nI genera,l increasi engt eh siz fo minimumcontentionwindoww illsignificantlyenhance t eh networkthroughput da n reduceconflictsunder et h condition fo congestion.T helocation fo each

e d o

n ni WSN nc ea b represented yb et h structure ni Figure1, ot which et h channeldistribution [ 11 ]i s d

e t a i c o s s

t r o p s n a r

t layer ni which et h node si located, thus et h minimum contention window fo et h node si d

e t a l u c l a

c according ot et h number fo childnodes da n minimumcontentionwindow fo et h layer.

e r u g i

F 1. Wireles ss ensor networks n eo l dd o da istribution.

r e y a

L MinimumConten itonWindow

e h

T calculationmethod fo layerminimumcontentionwindow si as followi : ng

(

)

(

)

n i m

0 0

n i m 1

n i m

   

< < +

∗

= +

∗ =

+

M i N W

C

i N W

C W C

i i

i

γ γ

( 1)

e r e h W

. | | / | |

/ g

o l

1

1

1

1 0

n i m 1

(

    

= =

∑

∑

=

−

= +

M

i

M

j i N

L N

N

M C K

M γ

( 2)

g n i m u s s

A there si a M-level tree, 0 n i m

W

C i est h value fo minimum contentio n window fo et h root e

d o

n ; _CWi

n i

m i est h value fo minimumcontentionwindow fo et hh i t layer; Nii est mh su fo et bh s -u nodes

f

o la el t h nodes ni et hh i t layer; N_i is et h averagevalue fo et h number fo bs -u nodes fo la el t h nodes ni

e h

t hi t layer; Ni est h averagenumber fo bs -u nodes ni et h network;γ i nsa adjustmentcoefficient, h

c i h

w si a fixedvalue rf o nodes ni et h samelayer; K si a constantgiven yb et h network state; L si et h m

u

s fo la l nodes ni et hh i t layer.

e d o

N MinimumConten itonWindow

n

I et h transmission tree, each nodereceives da n forwards different loads because fo et h different r

e b m u

n fo bs -u nodes.Therefore, et h minimumcontentionwindow fo each on ed should eb calculated d

e s a

b no et h number fo bs -u nodes da en t h layerminimumcontentionwindow.Calculati onmethod si

(

)

(

)

  

 − + ∗

=

−

i

i i i

n i

W C

W C D e D W

C n

n i m

n i m 1

, n i m

1 α

,

. 1 0

1

≤ ≤

<

n n

α

α _{( 3)}

(

)

(

)

γ − + = _i

i N

D )( 4 e

r e h

w α_n si et bh s -u nodes coefficient, obtainedfrom et h ratio fo et uh n mber fo la bl s -u nodes fo eo n e

d o

n ot et h averagenumber fo bs -u nodes ni et h layer; D_i si et h coefficient rf eo t h layer, to ensurethat e

h

t value fo nodeminimumcontentionwindow si between sthi layer da en t h upperone.

d e z i m it p

O T-MACProtocol

m h ti r o g l

A fo Conten itonWindow

n

I T-MACprotoco ,lBEBalgorithm si applied ot calculateback- fo f time fo eachnode. nI et h view fo y

c n e i c i f e

d fo ,ti et h advanced idea si proposed no et h basis fo et h lasttransmission fo et h node ot e

z i m i t p

, d e v i e c e

r which nc ea b consideredleading ot et h collision ni channelbecause of narrowwindow da n r

e w e

f interceptingtimes. Otherwise, fi et h transmission si completed, ti nc ea b considered that et h n

o i t n e t n o

c window si excessivel y wide, os that ti si unnecessary rf eo t h node ot intercepting et h l

e n n a h

c rf o multipletimes da en t oh c ntentionwindowm eayb lessene dappropriately.T healgorithm s

i e d o

N transmission ta et h lasttime

2

l i a f

: l u f s s e c c u s

o

o

W C W C

A W C W C

∗ = 

 _{= ∗}



: _{( 5)}

n

I et h formulaabove, CW is et h size fo contention window after et h information successfully d

e t t i m s n a r

t ro reconstructedafter et h collision; CW_oi est eh siz fo et h originalcontentionwindow; A si e

h

t coefficient ot minimize et h windowrapidly,configured sa lfo lowing:

x a m n

i m

x a m x

a m

x a m 2

1

1

8 1 1

1 ,

4 8

2

1 1

4 2

o

o

o

W C W C W C

W C W C W C A

W C W C

 _{< <} 



 _{< <}

=  

 _>



,

,

. ( 6)

s

A nc ea b seen from et h formulaabove, et h algorithmappli eest h coefficient ot alter et h optimal n

o i t n e t n o

c windo w size according ot t he condition fo network congestion. This mechanism s

e m o c r e v

o et h shortcoming that et h window si aboveextensive ro narrow, resulting ni et h energy .

n o i t p m u s n o

c Through keeping dynamic changes a nd coordinati ng w ith real-time network r

tansmission,networkbandwidth da n channelresources nc ea b madef ullu se.

d e v o r p m

I T-MACProtocol

n

I T-MACprotoco ,lvariable'TA' si introduced sa a bufferbetweenlistening da n sleepingtime.T he e

u l a

v si constrained as TA>C+R+T_{. rF eo t eh g neralnetwork, et h optimalvalue fo 'TA' si}

(

)

A

T =1.5 + + ( 7) d

e s a

B no et h minimum contention window obtained above, this cse tion presents na improved l

e d o

m ni terms fo 'TA'

(

)

5 .

1 ∗ min+ +

= ,in

A

T ( 8) n

I et h formulaabove, et h competitionintervalC si et h product fo et h s lottime da en t h minimum t

n o

c ention window. Time rf o sending et h RTS packet si determined yb et h core function ni et h n

o i t a l u m i

s too.l T he short-time interval T si equal ot et h short-frame interval SIFS. This formula s

e d i v o r

p a further energy saving em chanism rf eo t T-h MAC protocol ht rough supplementi eng t h n

o i t c u d e

r time fo et h listening period ot et h sleeping period. Dynamic listening/sleeping time rf o T-MACprotocol da en t h improved eo n havebeencompared ni figure2.

e r u g i

Simula iton da n ResutlsAnalyssi

F ro et h sake fo analyzing et h improvement fo et h network performance brought yb et h proposed m

h t i r o g l

a under different network conditions, thispaper utilizes et h tool OPNET ot establish et h n

o i t a l u m i

s model da n simulate et h network performance ni terms fo three network indicators fo ,t

u p h g u o r h

t energyconsumption da n timedelaytowards et h originalprotocol da n proposedone. e

h

T experimentalnodes ea r deployed ni a rectangulararea fo 100m×100m. T henode sh a single p

o

h communication a end t h communication radius si 50m. There ea 0r 2 sensors ni et h whole k

r o w t e

n da n each fo ti si fo samesetting. eT h dataframepayload si 1000bytes da en t h frameinterval s

i 02 µs. According ot et h experiment results ni reference [12], et h simulation parameters ea r d

e r u g i f n o

c sa shown ni bT . .a 1 Afterestablishing WSNparametermodelabove, eo fn o et h nodes si y

l m o d n a

r selected ot compare et h performancebetweenoriginal T-MAC w eith t h improved eo nn i s

i h

t article.

e l b a

T .1 Parametersetting.

r e t e m a r a

P Value Parameter Value

K C

A 1 [12btis] CW_min 3 [2slots] S

T

C 1 [12btis] CWmax 1024[slots]

S T

R 1 [60btis] ChannelRate 1 [Mbps] S

F I

S 1 [0 µs] Times lotLength 2 [0 µs] S

F I

D 5 [0 µ_s] T heMaximumNumber fo Retransmissions 7[itmes]

3 e r u g i

F , Figure4 da n Figure5respectivelyshow et h characteristics fo networkthroughpu ,tenergy n

o i t p m u s n o

c na d timedelaytowards et h original T-MAC protocol againstimproved eo n w eith t h e

d o

n traffic ta different transmission rates. From et h simulation results, ti nc ea b seen that et h d

e s o p o r

p algorithmpresentshigherthroughputthan et h originalprotoco,l da en t h advantage si more s

u o i v b

o w eith t h increase fo sending rate. T eh idle listening a nd repeated retransmissions ea r e

m o c r e v

o ni thispaperreducing et h number fo collisions da n retransmissionseffectively, which si d

e t i f e n e

b from adjustment mechanism a nd definition fo variable 'TA' w eith t h flexibly adjusted g

n i n e t s i

l time. Attributing ot less waiting time ni buffer, time delay si rather short compared et h l

a n i g i r

o protoco.l T he analysis results show that et h algorithm appears apparent advantages ni r

e s n o

c vingenergy da in mproving et h efficiency fo networktransmission.

e r u g i

e r u g i

F 5. Timedelaysimulationresults.

Summary

n

I iv we fo et h shortcomings da n deficiencies fo T-MAC, sthi paperproposes an optimizationmodel d

e s a

b no et h minimumcontentionwindow ni accordancew eitht h characteristics fo limitedresources d

n

a dynamicnetworktopology ni WSN. eT h calculatingmethod fo ht e minimumcontentionwindow f

o et h node si proposedaccording ot et h layer da bn s -u nodes fo et h networkstructure.Furthermore, n

o i t n e t n o

c window si optimizedtheoretically, os that ti nc a dynamicallyadapt ot et h requirement fo k

r o w t e

n transmission under et h condition fo congestion. Additionally, variable 'TA' ni T-MAC l

o c o t o r

p si relocated.Finally, experiment si implemented no et h simulationtool ot demonstrate et h y

t i l i b a c i t c a r

p fo et h conception ni thispaper. Simulation results show that this scheme achieves a r

e t t e

b performancethan et h original T-MAC protocol ni terms fo throughpu ,tenergyconsumption d

n

a time delay. Furthermore, energy consumption caused yb conflicting retransmissions da n idle g

n i t p e c r e t n

i si economized; therefore et h networkperformance sh a beenimproved.

Acknowledgem ent

s i h

T research w as financially supported yb et h National Natural Science Foundation fo China ;

) 7 1 0 1 6 4 1 6 . o N

( t he Hainan Natural Science Foundation Innovation Research Team Project ;

) 4 0 0 0 D T X C 7 1 0 2 . o N

( t he Innovative Research Project fo Postgraduates ni Hainan Province .

o N

( H s 1y 2 7- 00 1 ); et O nh p Te opic fo StateK eyLaboratory fo MarineResourcesUtilization ni South a

n i h

C aS fe o HainanUniversity(No.2018012); CollaborativeInnovation Fund fo TianjinUniversity & HainanUniversity(No.HDTDU201810).

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